A) Morinehtar and Romestamo. All wizards had many names, but these were the two names that most peoples of Middle Earth would use.
B) Galadriel is Elrond's mother-in-law.
C) Eagles would have been too conspicuous, and would have been spotted by Sauron. Recall that the eagles were able to rescue Sam and Frodo only after the Ring was destroyed and Sauron's power (and his body) were gone.
D) The waterfall conceals the secret entrance to Henneth Annun, a hidden refuge used for rangers. Gollum was really in trouble for entering the Forbidden Pool at the bottom of the waterfall. The penalty for entering the Forbidden Pool was death, since from there one might discover the secret entrance.
E) Denethor had suffered depression ever since the death of his wife, about 30 years before the events of LOTR. After that time, he secretly used a Palantir to spy on Sauron, and his depression worsened as he saw how powerful Sauron was becoming. Sauron in turn used the Palantir to drive Denethor further into depression and make him more than a little insane. His madness got even worse when his oldest son, Boromir, died. The injuries to his other son, Faramir, were the last straw. Denethor thought Faramir's injuries were fatal, and utterly despairing of any hope of surviving Sauron's onslaught, saving Minas Tirith, or leaving any progeny, he opted to commit suicide.